What is already known about this subject• The low-income subsidy (LIS) program was developed to offer financial assistance to Medicare beneficiaries with low income and assets by reducing their premiums and/or copayments.• Previous studies have identified factors associated with medication adherence and nonadherence, such as age, sex, race/ethnicity, and socioeconomic characteristics.• Less is known about the factors associated with medication nonadherence, specifically in the Medicare LIS population. What this study adds• Individual and community characteristics are associated with the likelihood of medication nonadherence among Medicare LIS recipients with type 2 diabetes, hypertension, or heart failure.• The following factors are positively associated with medication nonadherence: male sex, younger age, racial/ethnic minority status, living in a metropolitan statistical area or health professional shortage area, living in West or South regions, and a higher risk adjustment summary score.• This study provided insight into medication nonadherence within the Medicare LIS population and identified the need to consider these factors when developing future policies to improve medication adherence.